No agreement for the rotation of water shall in any manner impair or affect the rights of any prior encumbrancer of lands theretofore customarily irrigated by any part of the waters mentioned in such agreement, he not being a party to such agreement; nor shall such agreement, or the rotation of the waters pursuant thereto, in any manner affect or impair the rights or the priority of right of the parties thereto, or the persons using or entitled to use the waters referred to in such agreement, or any of them, as against other persons.